hogumathi-app/hogumathi_app/content_system.py

"""

A registry for content sources that work in terms of the View Model (view_model.py).

Generally a source returns a CollectionPage or individual items.

At present many sources return a List of Maps because the design is being discovered and solidified as it makes sense rather than big design up front.

May end up similar to Android's ContentProvider, found later. I was 
thinking about using content:// URI scheme.

https://developer.android.com/reference/android/content/ContentProvider

Could also be similar to a Coccoon Generator

https://cocoon.apache.org/1363_1_1.html

Later processing in Python:

https://www.innuy.com/blog/build-data-pipeline-python/

https://www.bonobo-project.org/

"""

import re
import inspect

content_sources = {}

hooks = {}

def register_content_source (id_prefix, content_source_fn, id_pattern='(\d+)', source_id=None):
    if not source_id:
        source_id=f'{inspect.getmodule(content_source_fn).__name__}:{content_source_fn.__name__}'
    
    print(f'register_content_source: {id_prefix}: {source_id} with ID pattern {id_pattern}')

    content_sources[ id_prefix ] = [content_source_fn, id_pattern, source_id]


def find_content_id_args (id_pattern, content_id):
    id_args = re.fullmatch(id_pattern, content_id)
    if not id_args:
        return [], {}
    
    args = []
    kwargs = id_args.groupdict()
    if not kwargs:
        args = id_args.groups()
    
    return args, kwargs
    
def get_content (content_id, *extra_args, **extra_kwargs):
    id_prefixes = list(content_sources.keys())
    id_prefixes.sort(key=lambda id_prefix: len(id_prefix), reverse=True)
    
    for id_prefix in id_prefixes:
        [content_source_fn, id_pattern, source_id] = content_sources[ id_prefix ]
        if not content_id.startswith(id_prefix):
            continue
        
        source_content_id = content_id[len(id_prefix):]
        
        print(f'get_content {content_id} from source {source_id}, resolves to {source_content_id}')
        
        args, kwargs = find_content_id_args(id_pattern, source_content_id)
        
        if id_prefix.endswith(':') and not args and not kwargs:
            continue
        
        if extra_args:
            args += extra_args
        
        if extra_kwargs:
            kwargs = {**extra_kwargs, **kwargs}
        
        content = content_source_fn(*args, **kwargs)
        
        if content:
            invoke_hooks('got_content', content_id, content)
            
            return content

def get_all_content (content_ids):
    """
    Get content from all sources, using a grouping call if possible.
    
    Returns a map of source_id to to result; the caller needs
    to have the intelligence to merge and paginate.
    
    Native implementation is to juse make one call to get_content per ID,
    but we need to figure out a way to pass a list of IDs and pagination
    per source; for exampe a list of 100+ Tweet IDs and 100+ YT videos
    from a Swipe file.
    """
    
    return get_all_content2(content_ids)
    
def get_all_content2 (content_collection_ids, content_args = None, max_results = None):
    """
    Takes a list of collection IDs and content_args is a map of (args, kwargs) keyed by collection ID.
    
    We could just use keys from content_args with empty values but that's a little confusing.
    
    Interleaving the next page of a source into existing results is a problem.
    
    Gracefully degraded could simply get the next page at the end of all pages and then
    view older content.
    
    We also need intelligence about content types, meaning perhaps some lambdas pass in.
    Eg. CollectionPage.
    
    See feeds facade for an example of merging one page.
    
    Seems like keeping feed items in a DB is becoming the way to go, serving things in order.
    
    Client side content merging might work to insert nodes above, eg. HTMx.
    
    Might be jarring to reader, so make optional. Append all new or merge.
    
    Cache feed between requests on disk, merge in memory, send merge/append result.
    
    """
    
    result = {}
    
    for content_id in content_collection_ids:
        if content_args and content_id in content_args:
            extra_args, extra_kwargs = content_args[content_id]
            
        result[ content_id ] = get_content(content_id, *extra_args, **extra_kwargs)
    
    return result

def register_hook (hook_type, hook_fn, *extra_args, **extra_kwargs):
    if not hook_type in hooks:
        hooks[hook_type] = []
    
    hooks[hook_type].append([hook_fn, extra_args, extra_kwargs])


def invoke_hooks (hook_type, *args, **kwargs):
    if not hook_type in hooks:
        return
    
    for hook, extra_args, extra_kwargs in hooks[hook_type]:
        hook_args = args
        hook_kwargs = kwargs
        if extra_args:
            hook_args = args + extra_args
        if extra_kwargs:
            hook_kwargs = {**extra_kwargs, **hook_kwargs}
            
        hook(*hook_args, **hook_kwargs)
        
        #try:
        #    hook(*args, **kwargs)
        #except TypeError as e:
        #    print ('tried to call a hook with wrong args. no problem')
        #    continue